<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <button>按钮</button>
  <script>
    const btn=document.querySelector('button');
    btn.onclick=()=>{
      console.log('00000');
    };
    btn.onclick=()=>{
      console.log('11111');
    };
    btn.addEventListener('click',()=>{
      console.log('222222',this);
    });
    btn.addEventListener('click',(e)=>{
      console.log('2222333',e.currentTarget);
    });
    btn.addEventListener('click',function(e){
      console.log('333333',e.currentTarget);
    });
    btn.addEventListener('click',function(){
      console.log('333333',this);
    });
  </script>
</body>
</html>